Sleep is an essential part of normal body function. It is cued by the release of a neurotransmitter chemical called adenosine. Other neurotransmitters, serotonine and norepinephrine, keep parts of the brain active while we are awake.

Although scientists have not found brain cells that get tired and ‘need’ to sleep, there appears to be some brain cells that work harder while we are awake while others work harder when we are asleep.

Unlike a baby who will sleep for up to 17 hours a day, an adult generally requires about 8 hours of sleep.

During sleep, you go through 5 or 6 sleep cycles. There are five stages to a sleep cycle:

Light sleep

Slower brain function with bursts of brain activity- adults spend 50% sleep time in this stage

Stages 3 and 4 combined make up ‘deep sleep’. It is hard to wake someone up from deep sleep and they will feel groggy and disoriented for several minutes after waking. Sound like anyone’s Monday morning?

We all know what happens when we spend too long without sleep. Lack of concentration, impaired memory and irritability are just some of the signs of fatigue.

Drowsiness, the last stage before sleep, is caused by the build up of adenosine in the brain. When a person has been awake for a long time, their cells release adenosine to signal a need for sleep.

Caffeine and other stimulants were shown in a 2005 study to interfere with adrenosine reaching the brain. This results in the brain being unaware that cells have been working for a prolonged time, delaying sleep.

Did you know that you develop a ‘sleep debt’ when going without sleep for prolonged periods of time? Although people may get used to a sleep-deprived schedule, their judgement, reaction time and other brain functions remain impaired. Eventually the body demands repayment of the sleep-debt.

Sleep deprived people who are tested with a driving simulator or a hand-eye coordination test often perform as badly as people who are drunk.

In the years between 2006 and 2010 in New Zealand, there were 937 vehicle crashes involving 1244 serious injuries and deaths. Although not as large as the number of crashes alcohol was involved in, any number of crashes attributable to sleep is too large. It is so simple to pull the vehicle over and take a 20 minute power nap. Arriving safely at a destination is preferable to not arriving at all.

Health benefits of sleep

Experiments have shown that sleep is linked with both a healthy nervous system and immune system.

In the nervous system, sleep is thought to give brain cells the chance to exercise brain connections that might otherwise deteriorate due to lack of activity.

In the immune system, deep sleep has been linked to the release of growth hormones in children and young adults. Proteins crucial for cell repair are produced in greater quantities during sleep.

The sleep-wake body clock

Our bodies are programmed to sleep at a certain time. Have you ever crossed a time line? Jet lag, severe fatigue, is the result of a confused body clock.

This ‘body clock’ controls the rhythm of waking and sleeping. It is cued by external light, and bright lights can apparently reset the clock. Some doctors are using ‘light therapy’, shining bright lights on people for several hours before they want to wake up, to help people adapt to new time zones.

Many people with total blindness have life-long sleeping problems because their brains cannot be cued for sleep by light.

In Western Society, people are burning both ends of the candle at once. When sleep is so crucial for good health, it is worth investing in at least 8 hours of sleep each night.

Alcohol is a drug: the body behaves differently once alcohol has been consumed. Medicinal drugs have side effects enough that a prescription from the doctor is required to gain access to helpful drugs like inhalers.

So why is alcohol available in supermarkets? Does it not have as many harmful side-effects as helpful pharaceuticals?

Processing Ethanol

The alcohol consumed in such huge quantities in New Zealand, available from supermarkets, is ethanol. We use and abuse it carelessly. But what does it really do in the body?

Because alcohol is not a naturally produced substance in the body, it has to be processed to clear it out of the body systems. Chemistry is responsible for this process. Most of the ethanol consumed is oxidised first to acetaldehyde, then to acetic acid. This chemical reaction happens primarily in the liver.

Although acetic acid is harmless, acetaldehyde is toxic. Should a person drink lots of alcohol, lots of acetaldehyde will build up. The build up of this toxic compound can cause severe discomfort, nausea and vomiting.

The alcohol not processed in the liver is excreted in sweat, urine or given off in breath. The alcohol content of exhaled air accurately reflects the alcohol content of the blood. This is the basis for breath-tests conducted by police.

Effect on the brain

Alcohol causes brain impairment in many ways.

Directly, it works as a depressant to decrease the activity of the nervous system. The effects of this are sometimes seen as increased activity, which seems counter-intuitive. In fact while the brain is normally functioning, it controls all body activity and will inhibit some of the possible activity. Alcohol decreases the brain’s control, allowing uncontrolled energy use.

As discussed in the Alzheimers and Memory post last week, brain cells communicate with each other via electrical and chemical signals using neurotransmitters. Alcohol has a direct impact on four neurotransmitters in the brain:

glutamate

gamma aminobutyric acid (GABA)

dopamine

serotonin

Glutamate is involved in learning and memory, while GABA is involved in motor control. Alcohol interferes with these neurotransmitters, preventing normal brain function. Dopamine and serotonin are normally involved in brain reward processes. Alcohol stimulates production of these neurotransmitters and uses them to cause the rewarding sensations associated with alcohol consumption.

Brain function can also be altered indirectly by alcohol. Alcohol will affect the immune system and cause production of hormones that end up in the blood transmitted to the brain. It’s ability to alter behaviour can also result in violent behaviour causing head injury.

General health implications

Excess alcohol consumption has been found to cause:

Brain damage

Brain disorder called Wernicke-Korsakoff syndrome

Cancer of the oesophagus, liver, colon and other areas

Dementia and memory loss

Depression and suicide

Heart damage

High blood pressure

Inflammation of the pancreas

Nerve damage

Sleeping problems

For a more complete list of problems, click here. To see an interesting page of alcohol-related facts, click here.

Drinking and driving: the lethal cocktail

New Zealand law does not allow drivers under 20 years old to drive after consuming any alcohol. Drivers older than 20 years have a blood alcohol limit of 400mcg breath or 80 mg blood, which (by my calculations) should equate to a BAC of 0.08%.

Because there are so many variables affecting the way the body processes alcohol, there is no easy way to quantify the amount of alcohol that can be drunk while maintaining enough brain control to safely -and legally- drive.

The safest rule: if you are going to drive, don’t drink.

Between 2006 and 2010 there were 2698 crashes involving alcohol. Many of these crashes involved impaired brain judgements in safe driving behaviour such as speed selection, overtaking and fatigue. There were 3565 serious injuries and deaths caused by these crashes.

Accidents caused by drink driving. Statistics courtesy of the New Zealand Transport Association.

Scientists have been trying to figure out how memory works for over a century. There is huge potential for such research to direct drug design for Alzheimers disease and other conditions involving memory loss.

There is no known cure for Alzheimers disease.

What is Alzheimers disease?

In Alzheimers, brain proteins form abnormal plaques and tangles, resulting in the death of brain cells and loss of memory. The protein changes are associated with a shortage of neurotransmitters, chemicals that convey messages between cells.

These neurotransmitters are very important and can be considered the ‘words’ of brain language.

The lack of neurotransmitter is addressed by drugs that treat symptoms of Alzheimers. One of these scarce neurotransmitters is acetylcholine. Several drugs focus on boosting existing levels of acetylcholine to address this chemical shortage.

Other drugs attempt to prevent further entrance of calcium into the brain. Excess calcium in brain cells damages them and causes a break-down in communication with other brain cells.

Memory Molecules

One of the challenges to understanding memory- and the brain in general- is that a mammal is estimated to have 1011 (100 billion) brain cells.

The regions of the brainSource: Creative Commons, artlessstacey

In a human, each of these neural (brain) cells is estimated to connect to 1000 other cells, meaning there are 1014 (100 000 billion) interconnections. These cell connections are called synapses and are structures that transmit chemical signals between cells. This communication involves a chemical neurotransmitter and specific regions of different calcium concentrations.

Recent research

There has been much study done to begin unravelling the memory mystery.

“Memory is produced when two neural cells interact in a way that somehow strengthens future signalling through the synapse.”

Donald O. Hebb, Canadian psychologist, 1949

Short-term memory

Following on from Hebb’s research, in 2007 Professor Joe Z. Tsien reported that a protein complex known as the NMDA receptor is responsible for strengthening future interaction between two neural cells. His research involved genetically engineering mice with no NMDA receptor and mice with enhanced production of the NMDA receptor. The mice with more NMDA receptors ‘learned faster and retained memories longer than unaltered mice did.’ He concluded that activation and reactivation of this NMDA receptor links memory from the molecular to the network level.

In 2009 further research was reported by Kenneth S. Kosik, a neuroscientist at the University of California Santa Barbara. He explained the strengthening of the synapse (join between two neural cells) as being the result of protein production. Proteins build the connection between brain cells and make it stronger.

Kosik found that the production of new proteins can only occur when a ‘silencing complex’ is turned off. When synapses are activated, one of the proteins wrapped around the silencing complex gets degraded. This allows the cell to start making these proteins to strengthen the neural connections.

Kosik was able to observe some of the specific proteins involved in building memory connections between brain cells.

Long-term memory

The strength of neural synapse connections is important but short-lived. Synaptic long-term memories are encoded at a deeper molecular scale. The enzyme CAMKII (Calcium/calmodulin-dependent protein kinase II) has long been recognised as a major player in long-term memory production.

In 2012 a group of scientists from the Universities of Alberta and Arizona looked at long-term memory coding using molecular modelling. They showed a spatial connection between microtubules and the enzyme CAMKII. Microtubules are major parts of the structural cytoskeleton within brain cells.

This group, including physicists Travis Craddock and Jack Tuszynski and anesthesiologist Stuart Hameroff, have demonstrated a mechanism for encoding synaptic memory into microtubules. They believe that memory is written into the cytoskeleton of brain cells.

Summary

There is on-going research aimed at untangling the mystery of memory formation and retention. Science is not yet in a postition to try to prevent Alzheimers or memory loss, but greater understanding of how memory works will help design drugs to that do this.

It is worth noting that there are ethical implications to understanding the formation of memory in the brain. As soon as science understands something, it tends to replicate it.